Fiber glass laminates containing furfuryl resin binder

ABSTRACT

GLASS FIBERS ARE BOUND WITH A FURFURYL ALCOHOL-FORMALDEHYDE RESIN IN A BINDER CONTAINING FURFURAL, A HIGH CATALYST LEVEL, AND A SILANE. THE RESULTING ARTICLE IS CURED AT TEMPERATURES BELOW 100*C.

United States Patent 3,681,286 FIBER GLASS LAMINATES CONTAINING FURFURYLRESIN BINDER Lloyd H. Brown, Crystal Lake, and David D. Watson,

Barrington, Ill., assignors to The Quaker Oats Coman Chicago, Ill.

Nd Df wiug. Original application May 31, 1968, Ser. No. 733,282. Dividedand this application Nov. 23, 1970, Ser. No. 92,228

Int. Cl. C08f 27/] US. Cl. 260-67 FA 1 ABSTRACT on THE DISCLOSURE Glassfibers are bound with a furfuryl alcohol-formaldehyde resin in a bindercontaining furfural, a high catalyst level, and a silane. The resultingarticle is cured at temperatures below 100' C.

CROSS-REFERENCES TO RELATED APPLICATIONS This application is a divisionof our previous application Ser. No. 733,282, filed May 31, 1968, nowPatent No. 3,594,345 entitled Fiber Glass Laminates Contain-- ingFurfuryl Resin Binder! BACKGROUND OF THE INVENTION The use of furfurylalcohol-derived resins as binders in glass fiber laminates is Wellknown. These laminates are appreciated in the industry because of theirhigh degree of chemical resistance. Consequently laminates bound withfurfuryl alcohol-derived resins 'find application in the fabrication ofindustrial vessels which are intended to contain highly corrosivechemicals such as acids and bases. However, the laminates which havebeen produced by heretofore available methods have not particularlydistinguished themselves with regard to structural strength.Consequently these laminates often found use in conjunction with otherhigh structural strength materials. It is an object of this invention toprovide a method for producing glass laminates bound with furfurylalcohol-derived resin, which laminates have high chemical resistance andmoreover have structural strengths which have been heretoforeunavailable with such resins.

SUMMARY OF THE INVENTION The method of this invention utilizes aresinous mixture of a specially prepared furfuryl alcohol-formaldehyderesin and furfural. We have discovered that the use of this specialbinder mixture, in conjunction with'unusually high catalyst levels andin conjunction with the presence of a silane, as a binder forglass-containing materials, provides structural strength heretoforeunavailable, when curing temperature is maintained below the boilingpoint of water. The special binder used in this invention comprises ahomogeneous mixture of (A) Furfuryl alcohol-formaldehyde resin having aviscosity between 5,000 and 200,000 cps., said resin having beenprepared by the steps of acid resinification of furfuryl alcohol andformaldehyde in a molar ratio of between 0.25 and 1.0 mole offormaldehyde per mole of furfuryl alcohol, neutralizing the catalyst,and removing substantially all water by distillation, and

(B) Furfural in an amount between 5 and 25 percent by weight based onthe weight of the composition, the resulting composition having aviscosity between 200 and 5,000 cps. at 77 F.

We have discovered that when this binder mixture is used in conjunctionwith high levels of catalyst, e.g. between 2 and 7 percent, preferablybetween 2.0 and 5.5

2 Claims 3,681,286 Patented Aug. 1, 1 972 percent, said catalyst beingselected from the group consisting of paratoluene-sulfonic acid, maleicacid, phosphoric acid, and acids of similar strength and also inconjunction with either vinylor amino-silane, objects of this inventionare achieved provided cure temperature is maintained below the boilingpoint of water. These objects include production of glass filled and/orreinforced materials having excellent structural strength, chemicalresistance, and heat stability. The flame resistance of structuresproduced in accordance with preferred embodiments of this invention isalso excellent. Moreover, shrinkage during cure is within ranges whichhave been heretofore reported for epoxy-bound laminates.

DESCRIPTION OF PREFERRED EMBODIMENTS In this invention we contemplatethe use of acid curable binder composition comprising a homogeneousmixture of (A) A furfuryl alcohol-formaldehyde resin having a viscositybetween 5,000 and 200,000 cps., said resin having been prepared by thesteps of acid resinification' of furfuryl alcohol and formaldehyde in amolar ratio of between 0.25 and 1.0 mole of formaldehyde per mole offurfuryl alcohol, preferably between 0.5 and 1.0 molar ratio,neutralizing the catalyst and removing substantially all of the waterproduced by said acid resinification, and

(B) Furfural in an amount between 5 and 25 percent preferably between 10and 20 percent by weight based on the weight of the composition, saidbinder composition having a viscosity between 200 and 5,000 cps. at 77F. preferably between 500 and 3,000 cps.

It is preferred that in the production of the curable binder compositionwhich is used in accordance with this invention, that furfuryl alcoholmonomer be removed from the furfuryl alcohol formaldehyde resin, e.g. byreduced pressure distillation after neutralization. We have discoveredthat furfuryl alcohol monomer contributes greatly to the development ofan undesirable exotherm within the fabricated laminate and to shrinkage.These undesirable attributes are minimized in accordance with thisinvention by initially preparing viscous resins, removing the furfurylalcohol monomer therefrom, and dissolving the resulting viscous resinsin furfural in amounts sufficient to provide between 5 and 25 percentfurfural, preferably between 10 and 20 percent, by weight based on theweight of the resulting composition. We have discovered that furfural isan excellent solvent for these resins as well as for the resins whichare conventionally used as a binder for glass fiber and cloth. Moreoverwe have found that substitution of furfural for the furfuryl alcoholmonomer in the furfuryl alcohol formaldehyde resins leads to very littleshrinkage providing the amount of furfural is held within the specifiedlimits. Moreover, we have discovered that the furfural used inaccordance with this invention becomes incorporated into the curedstructure.

As indicated above, the ratio of formaldehyde to furfuryl alcohol in theresin production method can be between 0.25 and 1.0 mole. Above thislevel odor becomes a serious problem during subsequent use of the resin,and below this specified level reactivity falls off rapidly. While 1t ispossible, under extremely carefully controlled conditions, to producelaminates with furfuryl alcohol resins which contain no formaldehyde atall, the handling properties of such materials were found to be poor andthe resins could not tolerate enough acid to achieve a good cure at highstrength without developing too much exotherm.

While we do not want to be bound by any theories we believe that theextremely high activity of furfuryl alcohol resin systems heretoforeused in the fabrication of laminates led to the development of excessiveexotherms thereby causing the resulting laminate to be weakened bysplitting or separating of laminate layers due to steam and gasevolution. It is to be noted that in the resinification of furfurylalcohol-derived resins water is produced. Consequently, based on ourintensive research, We now believe that in any method of producingfurfuryl alcohol resin bound laminates in which temperatures above theboiling point of water are encountered prior to the substantial curingof the binder, steam is evolved and bubble formation and laminateseparation is most likely encountered. Thus it is essential thattemperatures above the boiling point of water be avoided prior tosubstantial cure of the bound article.

In accordance with this invention, we prefer low viscosity materials,preferably around 500 cps. for use in most hand-layup laminate work. Wehave discovered that the method of this invention leads to considerablyless shrinkage and exotherm even when suchlow viscosity materials areemployed. Viscous resins are not particularly suitable in hand layupwork insofar as they are not well adapted to wetting of the glass fibermat. Viscous resins tend to be so tacky that they cause fibers to buildup on the roller, and entrained bubbles are almost unavoidable.

However, in some applications, e.g. in filament winding, higherviscosity resins are preferred. For these applications, we prefer bindercompositions of this invention which are essentially free of furfurylalcohol monomer. For such application we prefer to prepare the resin byresinifying the furfuryl alcohol-formaldehyde mixture to the desiredviscosity, neutralizing the catalyst, distilling off the water andfurfuryl alcohol monomer under reduced pressure and adding furfural tothe resulting viscous resin in an amount approximately equal to theamount of the furfuryl alcohol removed. When a 300 gram batch of a resinproduced in this manner is catalyzed in a paper cup by the addition of5% phosphoric acid, the resulting mixture gave a peak exotherm of only234 F. The resin mixture hardened without foaming or spalling. Incomparison to this a similar test with a resin from which the furfurylalcohol had not been removed gave a peak exotherm temperature of 311 F.During the hardening, the latter material popped and emitted a lot ofsteam. In contrast to both of these, conventional furfuryl alcoholpolymers expand many times during such a test to form a brittle foam, asa result of the copious quantities of steam emitted during theexothermic resinification of the resin.

It will be appreciated by those skilled in the art that the abovedescribed paper cup tests are useful insofar as they serve to indicatethe relative activity of the resin system employed. When the testedresins are permitted to resinify in thin sheets or under othercircumstances in which the evolved heat is dissipated, the test peaktemperatures recited above will not be encountered, and the resultingcured resin will not necessarily be in the same condition as the resincured in accordance with the paper cup tests described above.

The method of this invention can be utilized in conjunction With fibrousglass such as the conventional glass mat or conventional glass cloth; orit can be used in conjunction with fillers such as silica flour. In thefollowing examples, it will be illustrated that the method of thisinvention can be used in conjunction with the fabrication of laminatesproduced from glass mats and Fiberglas cloth, and in conjunction withthe so-called gunk molding processes and extrusion.

CATALYST The resin composition of this invention is cured by thepresence of an acidic catalyst. The preferred catalysts arep-toluenesulfonic (PTSA) and phosphoric acid. For use in accordance withthis invention, these acids must be added in the form of dilutedsolutions. The maximum concentration of solutions of preferred catalystis 70%; preferred concentration being about 67%. Water and alcohol arethe preferred catalyst diluents. Whatever acid is used however must beused in relatively high 'levels, e.g. between 2 and 7 percent. It isnoted that at these levels the catalysts produce an exothermic reactionin the binder resin of this invention. However, it should be noted thatthe exotherm of this composition is less than the exotherm encounteredin most catalyzed polyesters under similar test conditions. However,under the conditions of preparing a laminate in accordance with thisinvention the resin will be spread in relatively thin layers and willgel smoothly, that is, without expansion or foaming, in a relativelyshort period of time. The resulting laminates can be stripped, that is,removed from the shaping surface, without external heat, in a period oftime ranging from a few minutes to 2 hours. They will cure to a maximumstrength in about a month if room temperature curing conditions areprovided, or within a few hours if temperatures in the order of F. areprovided. An alternative technique for curing the glass-filled orreinforced structures made in accordance with this invention, is themethod in which the exterior of the shaped laminate or glass-filledstructure is heated to initiate an exotherm at the surface thereof andto cure the surface thereof, the shape being subsequently removed fromcontact with an external heat source. In this technique the initialexotherm is sufiicient to provide useful rapidly curing high temperatureconditions throughout the .entire laminate or filled shape. Within thelimit of an operators ability to manage the exothermic systems, higheststrengths are achieved when highest catalyst levels are employed. Usingthe method of this invention flexural strengths of 35,000 p.s.i. areachieved using glass mats and fiexural strengths in the order of 60,000p.s.i. are achieved using glass cloth.

Hence, the most highly catalyzed systems, in accordance with thisinvention are very exothermic. They can be used only in small batches,with cooling, or with some sort of a continuous mixing and coolingdevice. The actual amount of cooling required is not great, however. Forexample, if a 250 gram batch of resin is cooled to 70 F., and held atthat temperature while catalyst is added, the pot life will be between10 to 15 minutes without additional cooling. Without any cooling,however, the pot life of 21.10 gram batch using the same catalyst isapproximately 1 to 2 minutes. Nonetheless, the extremely short pot lifeof these highly catalyzed systems is entirely practical when the systemis used in the preferred method of handling systems of this type, thatis, in continuous methods such as those using a spray gun whichcontinuously mixes catalyst and resin in the spray head of the device.Such devices are conventional in the polyester field, and theconventional equipment can be used in this invention.

One outstanding advantage of the paratoluenesulfonic acid catalystsystem is that the resulting laminates do not necessarily have to befully cured before they are put in service. The laminates which arecured with this catalyst continue to cure even when immersed in boilingwater. Laminates which had been cured to about 10,000 p.s.i. flexuralstrength before the test, came up to 17,000 p.s.i. flexural strengthafter 24 hours immersion in boiling water.

This pattern does not hold true, however, for the phosphoricacid-catalyzed systems. We have not encountered a single instance inwhich a phosphoric acid-catalyzed structure increased in strength duringsuch a test. For example a laminate which was cured to about 14,000p.s.i. strength fell off to 9,000 p.s.i. under the same boiling watertest. However, when adequately cured, the structures pro duced inaccordance 'with this invention still appear better with respect to thisboiling water test than most general purpose polyesters.

An important advantage of phosphoric acid catalyzed systems is the easeof handling, i.e. management. Al-

though phosphoric acid is used in the same levels as paratoluenesulfonicacid, it provides considerably greater moderation in terms of exothermicreaction. Without cooling, gallon sized batches of the resin containingphosphoric acid (as a 67% solution in methanol) will give a pot life of30 to 45 minutes. Laminates produced with such a resin can be laid up inlayers as thick as one-half inch and then placed directly in an ovenwithout untoward eflect. With the oven at 120 F. the resulting laminatecan be stripped in less than one hour. If an oven is not available, thelaminate may be stripped after standing overnight at room temperature.Laminates produced with the phosphoric acid catalyzed resins of thisinvention will normally attain strengths of around 25,000 p.s.i. orgreater in about a Week at room temperature cure. I

SILANE FINISH The presence of reactive silanes, preferably, eithervinylor amino-silane, is essential in the method of this invention. Weprefer the use of substituted silane compounds in which the molecularweight of the silane moiety is less than 500. Glass fiber mats and clothare conventionally available with silanes on them as finishes becausethe addition of silanes to the glass fiber appears to be advantageous inthe manufacture of the glass fiber product, e.g. mat or cloth. If theglass fiber product utilized in accordance with this invention does notcontain a silane finish, it is essential that an effective amount of asubstituted silane, e.g. amino-silane or vinyl-silane be added to theresin binder. We have found that addition of a silane in an amountbetween 0.25 and 3 percent based on the weight of the binder compositionis entirely satisfactory in the method of this invention. We find thatin the absence of a silane finish even the preferred resins of thisinvention ha-ve'poor adhesion to glass. On the other hand addition ofthe 1% amino-silane to the resin of this invention leads to a binderwhich tenaciously adheres to glass. For example a laminate laid up onplate glass using the resin of this invention with 1% amino-silanecannot be stripped from the glass without chipping the glass.

It is to be noted that in the manufacture of glass fiber mat it iscustomary to utilize a relatively small quantity of a dissolving typepolyester mat binder. This mat binder causes the glass fibers to adhereto one another thereby maintaining the structural integrity of the matprior to its use. The mat binder employed is preferably soluble in theresin subsequently used as the laminate adhesive. Generally speaking,glass mats and cloth using any mat binders which are soluble inpolyester laminate adhesives are eminently satisfactory for use inaccordance with this invention. We have found that most dissolving typesof polyester mat binders are very soluble in the special furantypelaminate adhesive of this invention. It is preferred that the mat usedin accordance with this invention have such an amount of mat binder thatit will lose no more than between about 3 and 4 percent by weight whenthe mat is burned off at 550 C.

We have found that glass fibers which are finished with chromiummethaerylate or other non-silane finishes cannot be used in accordancewith this invention unless a reactive silane, such as either vinyloramino-silane, is added to the resin.

In the following examples and throughout the specification parts refersto parts by weight and percent (or refers to percent by weight andtemperatures are expressed in degrees Farenheit, unless otherwiseindicated.

and aqueous oxalic acid (0.78 part) were mixed at room temperature in al5-gallon stainless steel kettle equipped with a steam jacket, stirrer,thermometer Well, and reflux condenser. The pH of the resulting solutionmeasured 1.95. The batch was heated over a period of 18 minutes to atemperature of 94 C., at which point mild reflux began. At this pointthe hot cup viscosity as measured by a Cenco consistency cup No. 27145was 37.0 seconds. The batch refluxed at 98-100 C. for a period of about88 minutes at which time it gave a hot cup viscosity of 47.2 seconds.The reaction mass was neutralized with 0.39 part of triethanolamine topH 6.0. At this point 2.5 parts of 40% urea solution were added, and thesetup was changed to allow vacuum distillation. The batch was distilled130 minutes at temperatures up to C. and pressures down to 35 mm. Hg.The undiluted viscosity at 25 C. was then 12,900 cps. After dilutionwith '24 parts of furfural, a viscosity of 445 cps. was obtained. Yieldwas 119 parts after the dilution.

Example 2 The purpose of this example is to illustrate another method ofpreparing a preferred binder for use in accordance with this invention.A relatively furfuryl alcohol monomer-free version of the resin producedin accordance with Example 1 was made by a similar procedure, exceptthat cup viscosity was carried from 42.8 seconds to 46.6 seconds, andfinal distillation required 5 hours at kettle temperatures up to 123 C.and pressures down to 35 mm. of Hg. About 21.5 pounds of furfurylalcohol were collected in the receiver during the last part of thedistillation. The viscosity of the resulting resin at this point was100,000+ cps. Total resin yield was 75.0 parts, and 25.5 parts offurfural were then added to give a total product yield of 100.5 parts.Viscosity after dilution was 1,600 cps.

Example 3 The purpose of this example is to illustrate a method ofpreparing a glass fiber mat laminate in accordance with this invention.A long Mylar sheet was laid out on a flat Working surface. The resin ofExample 1 was sprayed onto the Mylar sheet using a conventional resinsprayer of the type which mixes resin and catalyst in the spray head,and which is normally used in connection with polyester lamimating. Thecatalyst pressure was adjusted to provide PTSA in an amount equivalentto approximately 6% by weight based on the weight of the resin. In theapparatus used, the catalyst and the resin were mixed in the spray headand a fraction of a second elapsed prior to application of the resultingcatalyzed mixture on the Mylar sheet. It is noted that with thisparticular resin this amount of catalyst is sufiicient to initiate anextremely vigorous curing reaction. The resulting coating was permittedto cure for approximately 10 minutes during which time the coatinggelled to form an even sheet or layer. No foaming or blistering wasobserved. Such a coating is referred to as a gel coat in the laminatingart. One of the purposes of the highly catalyzed gel coat is to providea smooth finish at the exterior of the resulting laminate. Aconsideration which is perhaps more important to the fabricator is thefact that the highly catalyzed gel coat cures much faster than the massof the laminate would normally be permitted to cure. Consequently thelaminate structure can be stripped from the gel coat-contacting surfacein a much shorter time than an equivalent laminate to which a gel coathas not been incorporated. After the gel coat cured a thin layer of theresin produced in accordance with Example 1 was sprayed on top of thegel coat. During this spraying, however, the pressure on the catalystsystem was reduced so that the amount of catalyst admixed with the resinwas suflicient to provide approximately 3% of PTSA catalyst. A mat ofchopped strand glass (1 /2 oz.) was laid upon the wet resin. The mat wasrolled into the wet layer of resin with the use of a resin roller. Thisdevice is a conventional laminating tool consisting of a plurality ofadjacent circumferentially grooved aluminum discs freely rotatable abouta common axle. As a result of rolling the glass mat with the resinroller the mat is worked down into the wet resin layer until the resincompletely wets all of the glass mat. The glass mat used in this exampleis designated as M-700 and is an E glass having a vinyl-silane finishand a soluble polyester resin binder. When the first layer of glass matwas thoroughly wetted as a result of the rolling operation, theresulting materials were again sprayed with the resin produced inaccordance with Example 1 to which suflicient PTSA was added during thespraying to again provide approximately 3% catalyst in the resin layer.Again the steps of laying-on the mat, rolling the mat into the resin,spraying a third layer of resin adding a third mat of glass were carriedout so that 3 glass mats were worked into 3 alternate layers of resin.The resulting laminate was permitted to cure for approximately one-halfhour at room temperature after which it was stripped from the Mylarsheet. The stripped laminate, was placed into a 160 F. curing oven forapproximately 4 hours. After this cure the cured laminate was found topossess a flexural strength of about 14,000 p.s.i. The laminate wasreturned to the 160 oven for a total cure of approximately 24 hours atwhich time it was removed from the oven and again subjected to a testfor flexural strength. It was determined that the flexural strength was24,550 p.s.i. at this point. The remaining laminate was divided into twoportions and these portions were subjected to different heat treatment.The first portion was again placed in the 160 oven and permitted toremain there for a period of 30 days. After this heat treatment it wasfound that the flexural strength of the laminate so treated was 33,500p.s.i. The second portion of the laminate produced in this example wasplaced in a heat treating oven at 230 F. and permitted to remain thereinfor 30 days. After 30 days it was found that the flexural strength ofthe sample so treated was 35,100 p.s.i. The latter test shows thattemperatures in excess of the boiling point of water can be used aftersubstantial curing of the binder.

Example 4 The purpose of this example is to illustrate the effect ofextremely high temperatures upon the flexural strength of the laminateproduced in accordance with Example 3. A laminate produced by theprocedure of Example 3 was subjected to 24 hours cure at 160 F., atwhich time it was found to have a flexural strength of approximately25,000 p.s.i. The laminate was divided into three portions. Each of theportions was placed in a different oven overnight. The ovens used hadtemperatures of 635 F., 500 F. and 400 F. respectively. After 16 hoursresidence in their respective ovens the portions were found to have aflexural strength of 8,230, 8,230 and 20,100 respectively. The samplewhich was subjected to 400 F. heat treatment was returned to the 400 F.oven for a total treatment of 40 hours at that temperature at which timeit was found to have a flexural strength of 16,300. After this samplewas subjected to a total of 110 hours at 400 F. the flexural strengthwas found to be 8,180 p.s.i.

Example 5 The purpose of this example is to illustrate the fabricationof a laminate in accordance with this invention using glass cloth. A gelcoat was formed on a Mylar sheet as set forth in Example 3 then a layerof resin was spread on the gel coat. This resin was produced inaccordance with Example 2, but modified by the addition of 1%amino-silane thereto. Also, PTSA was added in sufficient amount toprovide 3% concentration of the acid based on the Weight of the resin. Asheet of glass cloth was laid on the liquid resin. This cloth was a 181glass cloth which had been heat cleaned. The cloth was Worked into thewet resin using a conventional resin roller. The steps of spreadingresin, laying a sheet of glass cloth, and working the sheet into theresin was repeated ten times to provide eleven alternate layers of resinand cloth. A thin top-layer of resin was added to the uppermostresin-wetted glass cloth. After an overnight cure at roomtemperature theresulting laminate was stripped from the Mylar sheet. Subsequentanalysis revealed that the resulting laminate contained 55 to 60 percentglass. After curing for two days at room temperature the laminate wasfound to have a flexural strength of 20,000 p.s.i. A second sheet oflaminate produced in accordance with this example was placed in a F.oven after it was stripped and permitted to heat cure for four hours at160 F. and was subsequently cured at 210 F. overnight. After this curingtreatment the laminate was found to have a flexural strength of 62,100p.s.i.

Example 6 The procedure of Example 5 was repeated using a glass clothpre-treated with silane. The binder was a mixture of a resin produced asin Example 1, except that a 0.5 molar ratio of formaldehyde tofurfurylalcohol was employed, and the final mixture, containing 21% furfural,had a viscosity of 750 cps. The catalyst used in the laminating step was67% phosphoric acid in methanol. Sufficient catalyst was incorporated toprovide 5% phosphoric acid. The laminate was cured overnight at roomtemperature, then 24 hours at F. The cured laminate exhibited a tensilestrength of 56,600 p.s.i.

Example 7 The procedure of Example 5 was again repeated in two separatetests except that in the first test no amino-silane was added to theresin. In this first test the resulting laminate was cured for fourhours at 160 F. and overnight at 210 F. The resulting laminate was foundto have a flexural strength of 33,500 as compared to the 62,100 achievedwhen 1% amino-silane was added. In the second test of this example theprocedure of the preceding numbered example was again repeated exceptthat the catalyst level was 5% PTSA instead of the 3% of that example.After a cure of four hours at 160 F. and overnight at 210 F. theresulting laminate was found to have a flexural strength of 60,000 ascompared to 62,100 of Example 5. This illustrates that the additional 2%PTSA over the preferred 3% level provided no additional strengthadvantage in the fabrication of the glass cloth laminates.

Example 8 The purpose of this example is to illustrate the fabricationof a glass mat laminate in accordance with this invention and toillustrate the effect of excessively high curing temperature on thestrength of the resulting product. The resin produced in accordance withExample 2 was admixed with sufiicient PTSA to provide 3% acid based onthe weight of the resin. A thin layer of the resulting catalyzed resinwas distributed over the surface of the Mylar sheet and a 2 ouncechopped strand glass mat having a vinyl-silane finish was laid thereon.The glass mat was thoroughly worked into the resin layer using aconventional resin roller. A second layer of resin was distributed overthe resin wetted glass cloth and a second ply of 2 ounce glass mat wasworked into the second resin layer. These steps were repeated a thirdtime to provide a threeply laminate approximately one-eighth inch thickwhich was removed from the Mylar sheet after approximately 1 hour. Aftertwo days cure at room temperature the laminate was found to have aflexural strength of 24,100 p.s.i. The cured laminate was found tocontain 25% to 30% glass. In a separate test a laminate produced inaccordance with this example was subjected to a 24 hour cure at 165 F.instead of the 2 day cure at room temperature. In this test the flexuralstrength was found to be 28,100 p.s.i. In another repeat of this exampleexcept that the curing treatment of 16 hours at room temperaturefollowed by a post-cure of overnight at 250 F. was employed instead ofthe curing treatment used in the preceding test of this example thefiexural strength was found to be 21,000'p.s.i.

10 the stiif putty-like material. However when removed from the hotplate the biscuits had a tough skin on the bottom while the unheated topwas still cold. Exothermic heat Example 9 was observed to proceedthrough the mass of the specimen 1 5 and the hardened, i.e. cured, slowlwithout further ex- The Purpose of i example 18 Illustrate the ternal heating. At no time was any temperature at any the resmprodpced maccordance Wlth. Example 2.uSmg point in any biscuit of these testsobserved to be above phosphoric acid as a catalyst. The resin producedmac- C cordance with Example 2 was admixed with sufficient phosphoricacid (as a 67% solution in methanol) to pro- 10 Example 12 I I vide 5%of the acid catalyst based on the. weight of the v resin. The procedureemployed in Example 8 was repeated P P nP thls i 1S t 111usPrate cure toprovide a three-ply A; inch laminate of which contfichmqllqused 111 E p11 m conlunctlon 4 glass tained 25 to 30 percent glass. After 7 dayscure at room fiber lafljlflate- Va I IIS Samples of: three-ply F1berglastemperature the resulting laminate was found to have a 15 mat lammaiewere profiluced m a h Yesm of flexural strength of 24,000 p.s.i. When alaminate produced ample 1 f was modlfied by the addltlon f P by the samemethod was permitted to cure for 24hours at P t f a mat P Chopped glasswhlch 165 F. instead of the room temperature cure it' wastamedavmyl'sllane fimsh- Instead P found that the resulting product hada flexural strength nate to t room temPerature lmorfo PP from of 29 500psi r the Mylar, sheet, the laminate was sub ected to contact- 2 mg oftemperatures of'140 to 170 C. at the upper sur- Example face thereof forperiods of time of about 30 seconds. f, Exothermic heat was observed tomove through the cross The P p of this example to Illustrate the m ofsection of the resulting laminate with result that the envariousconcentrations of phosphoric acid on the flexural i the m was cured bythe exothermic a generated by strength of laminates produced inaccordance with this mthe polymerization f the resin It Should be notedvention when the resin produced in accordance with Exeven that theamount f heat evolved in these tests was ample 1 is used. Two separateportions of the resin pro insuhieient to provide temperatures above theboiling duced in accordance with Example 1 were admixed with. point f aphosphoric acid in suflicient amounts to provide 5% and v Example 13 7/2% phosphoric acid, respectively, based on the weight of the resin. Inthe tests of this example a layer of the Th purpose f thi example i toill the l. resins is spread on a Mylar sheet and 2 ounce glass mat l themical resistance provided by the laminates prois worked into thislayer of resin. It is noted that the glass d d i accordance ith hi i tiI a series of mat used in this example contained thereon a vinyl-silanefo te t various resins were t l d i h various finish. The steps wererepeated to provide a three-ply centrations of PTSA or phosphoric acid.The resin data inch thick laminate as in Example 8. The laminate was iummarized in Table 1. Three ply laminates were prostripped from theMylar after approximately two hours at duced as in Example 8 andsubjected to post cure, i.e. room temperature. In each of these tests aportion of the cure after stripping, at such temperatures and for suchlaminate so produced was cured for seven days at room times a are summai d i T bl 1, Aft th cure, th t mp r and a Second P of laminate W18 40flexural strength set forth in Table 1 in the column headed cured for 24hours at 165 F. The laminate produced with Flex. Str. were observed.Each of these laminates were the 5% catalyst resin showed aflexuralstrength of 26,400 then cut into strips which were then subjected to thep.s.i. after the seven day room temperature cure and action of a boilingliquid for 24 hours in various tests. 31,300 p.s.i. after the elevatedtemperature cure. The Water, acetone, 10% sodium hydroxide, and 35%sullaminate produced with the 7 /2 catalyst resin mixture phuric acidwere used as the boiling solvents. The flexural was found to provide aflexural strength of 22,000'p.s.i. strength (tested wet) was determinedafter 24 hours imafter seven day room temperature cure and 27,600 p.s.i.mersion in the boiling solvent. The strengths observed after 24 hours at165 are summarized in Table 1.

Y TABLE I.-OHEMICAL RESISTANCE All tests 24 hours at boilingpoint-tested wet Postcure Flex. Water Acetone Na l Run Percent str.,flex., fiex flex., flex., No. cat. Time Temp. p.s.i. p.s.i. p.s.i. p.s.ip.s.i

12-1 2.5 T 12.2". 5 P 3 .1%: it? 23:23 iiii i253; i312??? 1.8 T 25 days18,940 12-4-.- 5 I 35 days 75 24,425 14,080

Norn.Pj=HaPor. T=PTSA.

Example 11 Example 14 The purpose of this example is to illustrate anovel cure technique and the use of this invention in conjunction withsilica flour; The resin produced in accordance with Example 1 (250 partsof resin 404-194), 67 methanolic phosphoric acid (5% H PO based on theweight of the resin), 650 parts of silica flour, and parts of choppedglass fibers were blended to make a stiff putty-like material. It isnoted that the glass fibers contained thereon a vinyl-silane finish. Theresulting putty-like material was shaped cold into tensile strength testbiscuits which were divided into two test groups. The biscuits in thefirst test group were cured on a hot plate at C. (and in the second testgroup at 2203 C.) for a period of time between 10 to 30 seconds. It isnoted that this amount of time was The purpose of this example is tofurther illustrate the chemical resistance of laminates produced inaccordance with this invention and to compare it to the chemicalresistance of similar laminates not produced in accordance with thisinvention. The data obtained as a result of suflicient merely to heatthe outermost lower surface of 75 stance in which the letter F isincluded in the description column the resulting resin was diluted with15' parts of furfural per 100 parts of resin. It is noted that tests14-8 through 14-11 utilized binder compositions which were not dilutedwith furfural in accordance with this invention. In runs 14-14 and 14-15the (25%) indicates that furfural was present in an amount of 25 partsof furfural per 100 parts of resin. In runs 14-8 and 14-9 styrene ratherthan furfural is used to dilute the preresinified binder composition.Runs 14-10 and 14-11 utilized a binder composition which contained nodiluent whatsoever. The time set forth in the column headed Cure Cond.160 F. represents the amount of cure after the laminate was stripped.

12 in which the flame propagates along the laminate strip in the lastdescribed test even though the laminate retains its structuralintegrity.

The laminates produced in accordance with this invention appear to bevery stable with respect to heat. For example, a mat laminate with aninitial flexural strength of 29,400 had after 30 days at 110 C. aflexural strength of 30,700. By way of comparison commercial bisphenol Afumarate polyester laminates have been reported (R. F. Register,proceedings of the 22nd Annual Meeting of the Reinforced PlasticsDivision, SPI, Section 16D) to lose an average of 19% of their strengthfrom an initial average of 16,250 p.s.i. in 2 months at 110 C.

TABLE II Percent Percent Cure Orig. Acetone loss or H20 loss or RunComposition cond., flex., flex., gain flex gain number description 160F. p.s.i. p.s.i. p.s.i; p.s.i.- p.s.i.

14-1 0.25F 9 hrs- 16,350 14, 975 -8. 4 14, 950 --8. 57 0.2513 25 hrs.-.18,850 19, 550 +3. 71 22. 6 0.3751 9 hrs 18, 075 18, 975 +4. 98 16, 150-10. 65 0.3753 25 hrs.-. 17, 300 19, 825 +14. 6 17, 700 +2. 31 0.5F 9hrs..-- 20, 425 22, 575 +10. 55 16, 700 18. 25 0.51 25 hrs- 21, 07523,150 +9.85 000 -19.3 0.51 4 hrs 17, 750 13, 300 29. 1 16, 750 -5. 640.58 b 9 hrs--- 18, 750 21, 225 +19. 55 15, 800 ---15. 7 0.55 25 hrs.20, 600 15, 175 26. 3 15, 750 23. 5 178 9 hrs. 20, 050 13, 550 -32. 416, 200 19. 2 178 25 hrs.-- 20, 850 15, 425 26. 0 17,050 -18. 2 0 F-81 d4 hrs 15, 950 19, 925 +24. 9 14,450 -9. 4 .5F81 25 hrs--- 19,525 22,100+13. 2 17,950 8.07 14-14 0.5F (25%)81 4 hrs. 15, 850 19, 825 +25. 1 17,100 +7. 90 l-15 0.5F (%)81 25 hrs. 21, 200 25, 850 +21. 850 15. 8

a 0.251 means 0.25 mole of CHzO per mole of FA, cut back 15% withfurtural.

b S= Styrene.

B Resin 898-178 undiluted.

d Resin 398-81 (79,000 cps.) out back with 15% iurfural.

s Flexural strength (p.s.i.) after 66 hours in boiling acetone. 1Flexural strength after 69 hours in water at 200-210 F.

Except for those tests in which the resins were obviously under-cured,the laminates physical appearance was such that there was no apparenteffect as a result of the residence in the boiling medium, and thesolutions from which the test strips were removed remained light coloredand clear. In similar tests samples were retained in boiling water forone week and the results were not significantly different for the threeday values reported above in Table I. In all of the tests described inthe two preceding numbered examples one-inch by three-inch specimenswere employed, with edges unprotected. It is noted that the SPI standardtest for chemical resistant process equipment calls for protecting theedges of fiber glass laminates during similar tests.

We have found that all the laminates produced in accordance with thisinvention would be rated as nonburning by ASTM 635-63. However, thosemade with PTSA are not as fire resistant as the resins produced usingphosphoric acid as the catalyst.

In another laboratory test a three-inch by fourteeninch strip oflaminate prepared in accordance with this invention (with phosphoricacid catalyst) is suspended at an angle in a hood. The lower tip of thestrip is positioned so that the full flame of a diameter Bunsen Burnerwas in direct contact with the strip. After a full flame was played onthe under surface of the strip for about two hours, at the front of thehood and the bottom of the laminate, it was observed that virtually nosmoke had been evolved, that the fire which occurred initially in thelaminate in the immediate vicinity of the flame had extinguished itselfin two or three minutes and that the burned area after a period of threehours was restricted to a radius of about two inches in the immediatevicinity of the flame. The burner flame never penetrated the laminate,and the latter retained its structural integrity. It must be emphasizedthat this type of result is obtained only when phosphoric acid catalystis used in accordance with this invention. Use of PTSA as the catalystfor the binder composition results in a product At 400 F., whenprotected from oxidation, laminates produced in accordance with thisinvention lose strength very slowly. Over a period of hours the strengthdrops on an average to about 8,000 p.s.i. and appears to level out atthat value. The same phenomenon as observed overnight at 635 F.

Example 15 The purpose of this example is to illustrate the shrinkagecharacteristics associated with the. laminates produced in accordancewith this invention. A series of 8 tests was performed using-variousresin compositions produced in accordance with this invention. Variousamounts of furfural were used in preparation of these resins. The dataobtained as a result of this series of .tests is summarized in Table111. All the resins used in hyde per mole furfuryl alcohol at thebeginning of the preparation thereof, but had a viscosity too high to bemeasured by available equipment, that is, in excess of 100,000 cps. Theresin used in tests 15-3 and 15-4 was a blend of one part resin producedfor test 15-1, and two parts of a resin made in same Way with a 0.5molar ratio, but having an undiluted viscosity of only 2,400 cps.Viscosity of the undiluted blend was 8,300 cps. Resin used in test 15-5employed no formaldehyde during preparation thereof and had an undilutedviscosity of 47,000 cps. The resin used in test 15-8 was prepared with1% in the reactants which included 0.5 mole of formaldehyde per mole offurfuryl alcohol. Undiluted viscosity was about 42,000 cps.

The data included in the column headed percent Cat. indicates the levelof PTSA catalyst based on theweight of the resin. The data included inthe column headed Cure refers to the number of hours cure after 13stripping in an oven at the temperature indicated. It is noted thatthere are 3 pairs of columns headed Cure, and Shrinkage the pairs beingnumbered I, II, and III. This indicates that the shrinkage value setforth was the value observed after the specimen was cured under theconditions set forth in the corresponding cure column.

For the purpose of comparison it might be noted that epoxy resins havebeen reported (H. L. Parry and H. A. MacKay, 13th Annual Technical andManagement Conference, Reinforced Plastics 'Div., SPI, Section 13-A) toshrink up to 5.75% during cure at 65 C. With diethylene triamine at 25C., they shrank 4.3%.

In obtaining the data set forth in Example 3, shrinkage was determinedby casting bar specimens /2 inch by /2 inch by 5 inches, in a Teflonmold. One side of the mold was removable and resin was poured into theclosed mold from an opened end. With highly exothermic systems thespecimens were allowed to gel with some cooling, and then to hardenovernight. Finally they were cured for the specified number of hours atthe temperature indicated. Immediately after removal from the mold, thespecimens were measured with micrometers and from time to time themeasurements were repeated and the change in volume was calculated. Thedata set forth in Table III represents the change in volume.

Hence, from the above it will be appreciated that in accordance withthis invention laminates and other structures prepared with silica andglass fibers are produced with the result that unusually high structuralstrength, heat stability, chemical stability, and flame resistance areachieved.

Therefore, we claim:

1. An acid curable binder composition for use with glass-containingmaterials comprising: a homogeneous mixture of (A) a furfurylalcohol-formaldehyde resin having a viscosity between 10,000 and 200,000said resin having been prepared by the steps of resinifying in thepresence of an acid catalyst furfuryl alcohol and formaldehyde in amolar ratio of between 0.25 and 1.0 mole of formaldehyde per mole offurfuryl alcohol, neutralizing the acid catalyst and removingsubstantially all the water by distillation, and

(B) furfural in an amount between 5 and 25 percent by weight based onthe weight of the composition, said binder composition having aviscosity between 300 and 5,000 cps. at 77 F.

2. A composition as in claim 1 in which the furfnrylalcohol-formaldehyde resin has a viscosity between 10,- 000 and 200,000cps. at 77 F. in which the binder composition containing the fnrfuralhas a viscosity between 500 and 1,000 cps.

References Cited UNITED STATES PATENTS 8/1957' Harney 260 304 MORRISLIEB-MAN, Primary Examiner S. M. PERSON, Assistant Examiner US. Cl. X.R.

